Quantum Gravity: The Answer We've Already Found
Prof. John Donoghue explains how quantum physics and gravity fit together, covering quadratic gravity and effective field theory. 🌍

Curt Jaimungal
89.1K views • Dec 29, 2025

About this video
Professor John Donoghue explains why quantum physics and gravity actually work perfectly together. He tackles quadratic gravity, effective field theory, and random dynamics, arguing that grand unification and naturalness aren't required for a theory of everything.
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TIMESTAMPS:
- 00:00:00 - Limits of Quantum Mechanics
- 00:06:35 - Effective Field Theory
- 00:12:24 - Gravity: Geometry or Force?
- 00:18:46 - QFT and Gravity Tension
- 00:24:59 - Quadratic Gravity Theory
- 00:34:16 - Dueling Arrows of Causality
- 00:41:57 - Random Dynamics and Anti-Unification
- 00:48:13 - The Naturalness Problem
- 00:53:40 - Questioning Hidden Assumptions
LINKS MENTIONED:
- John's lectures: https://www.youtube.com/@johndonoghue469/featured
- John's papers: https://arxiv.org/a/donoghue_j_1.html
- The Renormalization Group and Critical Phenomena [Paper]: https://www.nobelprize.org/uploads/2018/06/wilson-lecture-2.pdf
- Anthropic Considerations in Multiple-Domain Theories [Paper]: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.80.1822
- Old "Ghost" Theory of Quantum Gravity Makes a Comeback [Article]: https://www.quantamagazine.org/old-ghost-theory-of-quantum-gravity-makes-a-comeback-20251117/
- Unitarity, Stability and Loops of Unstable Ghosts [Paper]: https://arxiv.org/pdf/1908.02416
- An Effective Field Theory of Gravity for Extended Objects [Paper]: https://arxiv.org/abs/hep-th/0409156
- Not Quite a Black Hole [Paper]: https://arxiv.org/pdf/1612.04889
- On Quadratic Gravity [Paper]: https://arxiv.org/pdf/2112.01974
- Quadratic Gravity [Paper]: https://arxiv.org/pdf/1804.09944
- Renormalization of Higher Derivative Quantum Gravity [Paper]: http://www.weylmann.com/stelle.pdf
- Quantum Theory in a Nutshell [Book]: https://www.amazon.com/Quantum-Field-Theory-Nutshell-nutshell/dp/0691140340
- Field Theory: A Modern Primer [Book]: https://www.amazon.com/Field-Theory-Modern-Frontiers-Physics/dp/0201546116
- Origin of Symmetries [Book]: https://amzn.to/4qxnLzj
- String Theory Iceberg [TOE]: https://youtu.be/X4PdPnQuwjY
- Neil Turok [TOE]: https://youtu.be/zNZCa1pVE20
- Avshalom Elitzur [TOE]: https://youtu.be/pWRAaimQT1E
- Sir Roger Penrose [TOE]: https://youtu.be/iO03t21xhdk
- Ted Jacobson [TOE]: https://youtu.be/3mhctWlXyV8
- Leonard Susskind [TOE]: https://youtu.be/2p_Hlm6aCok
- Jonathan Oppenheim [TOE]: https://youtu.be/NKOd8imBa2s
- Peter Woit [TOE]: https://youtu.be/TTSeqsCgxj8
- Joseph Conlon & Peter Woit [TOE]: https://youtu.be/fAaXk_WoQqQ
- Michael Levin [TOE]: https://youtu.be/c8iFtaltX-s
SOCIALS:
- Twitter: https://twitter.com/TOEwithCurt
- Discord Invite: https://discord.com/invite/kBcnfNVwqs
Guests do not pay to appear. Theories of Everything receives revenue solely from viewer donations, platform ads, and clearly labelled sponsors; no guest or associated entity has ever given compensation, directly or through intermediaries.
#science
I subscribe to The Economist for their science and tech coverage. As a TOE listener, get 35% off! No other podcast has this: https://economist.com/TOE
SUPPORT:
- Support me on Substack: https://curtjaimungal.substack.com/subscribe
- Support me on Crypto: https://commerce.coinbase.com/checkout/de803625-87d3-4300-ab6d-85d4258834a9
- Support me on PayPal: https://www.paypal.com/donate?hosted_button_id=XUBHNMFXUX5S4
JOIN MY SUBSTACK (Personal Writings): https://curtjaimungal.substack.com
LISTEN ON SPOTIFY: https://open.spotify.com/show/4gL14b92xAErofYQA7bU4e
TIMESTAMPS:
- 00:00:00 - Limits of Quantum Mechanics
- 00:06:35 - Effective Field Theory
- 00:12:24 - Gravity: Geometry or Force?
- 00:18:46 - QFT and Gravity Tension
- 00:24:59 - Quadratic Gravity Theory
- 00:34:16 - Dueling Arrows of Causality
- 00:41:57 - Random Dynamics and Anti-Unification
- 00:48:13 - The Naturalness Problem
- 00:53:40 - Questioning Hidden Assumptions
LINKS MENTIONED:
- John's lectures: https://www.youtube.com/@johndonoghue469/featured
- John's papers: https://arxiv.org/a/donoghue_j_1.html
- The Renormalization Group and Critical Phenomena [Paper]: https://www.nobelprize.org/uploads/2018/06/wilson-lecture-2.pdf
- Anthropic Considerations in Multiple-Domain Theories [Paper]: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.80.1822
- Old "Ghost" Theory of Quantum Gravity Makes a Comeback [Article]: https://www.quantamagazine.org/old-ghost-theory-of-quantum-gravity-makes-a-comeback-20251117/
- Unitarity, Stability and Loops of Unstable Ghosts [Paper]: https://arxiv.org/pdf/1908.02416
- An Effective Field Theory of Gravity for Extended Objects [Paper]: https://arxiv.org/abs/hep-th/0409156
- Not Quite a Black Hole [Paper]: https://arxiv.org/pdf/1612.04889
- On Quadratic Gravity [Paper]: https://arxiv.org/pdf/2112.01974
- Quadratic Gravity [Paper]: https://arxiv.org/pdf/1804.09944
- Renormalization of Higher Derivative Quantum Gravity [Paper]: http://www.weylmann.com/stelle.pdf
- Quantum Theory in a Nutshell [Book]: https://www.amazon.com/Quantum-Field-Theory-Nutshell-nutshell/dp/0691140340
- Field Theory: A Modern Primer [Book]: https://www.amazon.com/Field-Theory-Modern-Frontiers-Physics/dp/0201546116
- Origin of Symmetries [Book]: https://amzn.to/4qxnLzj
- String Theory Iceberg [TOE]: https://youtu.be/X4PdPnQuwjY
- Neil Turok [TOE]: https://youtu.be/zNZCa1pVE20
- Avshalom Elitzur [TOE]: https://youtu.be/pWRAaimQT1E
- Sir Roger Penrose [TOE]: https://youtu.be/iO03t21xhdk
- Ted Jacobson [TOE]: https://youtu.be/3mhctWlXyV8
- Leonard Susskind [TOE]: https://youtu.be/2p_Hlm6aCok
- Jonathan Oppenheim [TOE]: https://youtu.be/NKOd8imBa2s
- Peter Woit [TOE]: https://youtu.be/TTSeqsCgxj8
- Joseph Conlon & Peter Woit [TOE]: https://youtu.be/fAaXk_WoQqQ
- Michael Levin [TOE]: https://youtu.be/c8iFtaltX-s
SOCIALS:
- Twitter: https://twitter.com/TOEwithCurt
- Discord Invite: https://discord.com/invite/kBcnfNVwqs
Guests do not pay to appear. Theories of Everything receives revenue solely from viewer donations, platform ads, and clearly labelled sponsors; no guest or associated entity has ever given compensation, directly or through intermediaries.
#science
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Video Information
Views
89.1K
Likes
1.6K
Duration
01:03:38
Published
Dec 29, 2025
User Reviews
4.7
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